The present invention relates to a method of treating leaf tobacco for storage and, more particularly, to a process where the moisture content of the leaf tobacco is regulated to minimize or eliminate degradation of the leaves as a result of packing of the leaves for storage.
In U.S. Pat. No. 2,124,012, to Smith, Jr., of July 19, 1938, there is proposed a drying process for leaves packed in a hogshead where, in a preferred embodiment, the packed hogshead is subjected to a radio frequency field to heat the tobacco leaves while, at the same time, the leaves are subjected to a relatively high vacuum to cause evaporation of the moisture. As an alternative, it is suggested that the tobacco be successively subjected to the vacuum evaporation and the action of an alternating electro-static field for heating. The advantage of first tightly packing the tobacco in a container and then reducing its moisture content by the use of a high frequency potential difference is that the leaves could be dried for aging without handling the leaves which become very fragile as their moisture content is reduced. It is, of course, essential that during the aging process, which may be for a period of two or more years, that the tobacco leaves by dried to avoid deterioration during the aging process. However, reduction of the moisture content of the tobacco leaves, as noted above, renders them quite fragile so that any handling frequently results in breakup of the leaves and loss of an appreciable amount of the product. As a result, the filling power of the tobacco will be correspondingly reduced.
While the Smith, Jr. patent proposes a solution to this problem, it has been found that the combination of a high vacuum together with electromagnetic heating of the tobacco leaf, particularly where the stems remain in the tobacco leaves, can be very time consuming and costly. In many circumstances, due to the problem of arcing at a very low vacuum, only a very low power electromagnetic field can be employed thus greatly prolonging the drying process. In addition, the presence of stems in the leaves has been found to further prolong the drying process since the stems contain a significant portion of the moisture of each leaf.
It is, accordingly, an object of the present invention to provide a method of treating leaf tobacco which is significantly more efficient than the processes of the prior art both in terms of the production output of the process as well as an overall increase in the filling power of the tobacco product.
In summary, according to a preferred embodiment of the present invention, the tobacco is tightly packed in a container that is non-conductive and where the leaves of the tobacco have had their stems removed. The packed containers are then first subjected to a heat treatment by exposing the containers to an electromagnetic field produced by a radio frequency generator to heat the leaves to a temperature of approximately 180.degree. F. Thereafter, in the same or in a different chamber, the packed containers are subjected to a high vacuum to reduce the moisture content thereof and to reduce the temperature of the leaves. In some circumstances, it may be desirable to apply a low power electromagnetic field during the vacuum treatment to further reduce the moisture content of the leaves.
With the process of the present invention where the high temperature heat treatment precedes the vacuum treatment, the drying process can be effected for a packed container in substantially less time than was the case with the prior art processes where the heat treatment and vacuum were carried out simultaneously. By conducting the heat treatment at substantially atmospheric pressure, the problem of arcing in the electrical equipment was avoided.
The foregoing and other advantages of the present invention will become apparent as consideration is given to the following detailed description taken in conjunction with the drawing, in which: